The lens of the human eye is originally flexible and focuses for vision at different distances by deforming so as to change its thickness in the axial direction of the eye. For near vision the lens is relatively fat, or thick, and for distance vision it is stretched so that it becomes relatively thin. The lens cannot have a blood supply and consequently with age will tend to become stiffer and misty. As the lens becomes stiffer, the range of clear vision is reduced. This is why older people often require reading spectacles, bifocals or varifocals. The mistiness is cataract.
For the treatment of cataracts it is known to perform a surgical procedure in which the cataracted lens is removed from the eyeball through a small incision made in the wall of the cornea and replaced by an artificial intraocular lens. One known surgical procedure involves the extracapsular removal of the cataracted natural lens, leaving portions of the lens sac, or capsular sac, intact to hold the implanted intraocular lens. The intraocular lens is folded and inserted into the capsular sac where it unfolds. The intraocular lens has two side struts called haptics that press against the inner side of the capsular sac to hold the lens in place within the capsular sac.